Transcript for Russia Accused of Launching a Full-Scale Invasion of Ukraine

Martha, thank you. To the other major development overseas, Russia accused of launching a full-scale invax of Ukraine, the Ukraine government saying that Russian tanks have moved across the southeastern border. President Obama saying that Russia can no longer hide the fact that E they're supporting separatists in that region. Reporter: Plumes of smoke, as shells rain down. Ukraine's leaders are clear tonight -- this is a Russian invasion. Russian military boots are on Ukrainian ground. Reporter: Ukrainian forces today lost control of a border town, and nato says at least a thousand soldiers are inside the country fighting alongside and supporting pro-russian separatists. But today, the kremlin was in full denial mode. This satellite imagery, though, is hard to dispute. Nato claims it shows Russian artillery and troops moving inside Ukraine. What's clear is that there is now a war in Europe. It has escalated far beyond those fiery protests we witnessed on the streets of kiev earlier this year. What happens here is they light a molotov cocktail, throw it in the direction of the police, and then scurry back for protection. Reporter: Those protestors wanted closer ties with Europe, but Vladimir Putin never wanted any of that, and he is serious. Russia already annexed crimea back in March, and if rebel forces push further west, Russia might secure a strategically important land corridor all the way to the black sea. Up until a few hours ago, the U.S. And allies had struggled to find a united voice, to confront Putin directly over Ukraine. Russia has to stop lying. The cost of inaction is unacceptable. Reporter: Today, perhaps, is a turning point. Hamish Macdonald, ABC news. Back here at home, those two

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